Hybrid latch flip-flop

ABSTRACT

A hybrid latch flip-flop is applied to an LCD. The hybrid latch flip-flop includes a negative pulse generation unit, a latch flip-flop, and a buffer unit. The latch flip-flop includes a sampling unit and a hold unit. One feature of the present invention is that fewer transistors are employed in the hybrid latch flip-flop, which gives rise to low power consumption. Another feature of the present invention is that, by employing the negative pulse generation unit of a double edge trigger type, the data processing capacity of the hybrid latch flip-flop is doubled without changing the clock frequency.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a flip-flop. In particular, the present invention relates to a hybrid latch flip-flop.

2. Prior Art

The TFT-LCD is now gradually becoming a standard output apparatus for various digital products. However, the TFT-LCD still needs a proper driving circuit to let it work stably.

In general, the driving circuit of a TFT-LCD can be divided into two parts, one is the source driving circuit and the other is the gate driving circuit. The source electrode in the TFT-LCD is used for controlling the gray level of each pixel unit of the TFT. The gate electrode driving circuit is used for controlling the scanning of each pixel unit. These two kinds of driving circuit both apply shift registers as core circuit units. Latch units and flip-flops are the common choice for use as the shift registers. There are many kinds of flip-flops, such as the SR flip-flop, the JK flip-flop, the D flip-flop, and the T flip-flop. In these kinds of flip-flops, the D flip-flop is commonly used as the shift register. That is to say, the D flip-flop is always used as the core circuit unit in the TFT-LCD driving circuit.

However, the D flip-flop according to the prior art still has many disadvantages. It has a long transition period and easily shifts the clock period. For this reason, people skilled in the art have developed a hybrid latch flip-flop for solving the above problems.

Referring to FIG. 11, a hybrid latch flip-flop is disclosed by H. Partovi, R. Burd, U. Salim, F. Webber, L. DiGregorio, and D. Draper in “Flow-through latch and edge-triggered flip-flop hybrid elements”, published in ISSCC Dig. Tech. Papers, February 1996, pp. 138-139. The hybrid latch flip-flop 100 according to the prior art comprises a clock input 101, an inverter unit 110, a latch flip-flop 130, a buffer unit 150, a data input 103, and a data output 105. The latch flip-flop 130 comprises a data sample unit 140 and a data hold unit 149.

The inverter unit 110 comprises a first inverter 111, a second inverter 112, and a third inverter 113. The input of the first inverter 111 is connected to the clock input 101. The output of the first inverter 111 is connected to the input of the second inverter 112. The output of the second inverter 112 is connected to the input of the third inverter 113. The output of the third inverter 113 is connected to the latch flip-flop 130.

The data sample unit 140 comprises four PMOS type transistors and six NMOS type transistors. The four PMOS type transistors comprise a first PMOS type transistor 131, a second PMOS type transistor 132, a third PMOS type transistor 133, and a fourth PMOS type transistor 134. The six NMOS type transistors comprise a first NMOS type transistor 141, a second NMOS type transistor 142, a third NMOS type transistor 143, a fourth NMOS type transistor 144, a fifth NMOS type transistor 145, and a sixth NMOS type transistor 146. The sources of the four PMOS type transistors are connected to a power source 104. The gate of the first PMOS type transistor 131, the gate of the first NMOS type transistor 141, and the gate of the fourth NMOS type transistor 144 all are connected to the clock input 101. The gate of the second PMOS type transistor 132 and the gate of the second NMOS type transistor 142 all are connected to the data input 103. The output of the third inverter 113 is connected to the gate of the third NMOS type transistor 143, the gate of the sixth NMOS type transistor 146, and the gate of the third PMOS type transistor 133. The drain of the first PMOS type transistor 131 is connected to the drain of the first NMOS type transistor 141, the drain of the second PMOS type transistor 132, the drain of the third PMOS type transistor 133, the gate of the fourth PMOS type transistor 134, and the gate of the fifth NMOS type transistor 145. The source of the first NMOS type transistor 141 is connected to the drain of the second NMOS type transistor 142. The source of the second NMOS type transistor 142 is connected to the drain of the third NMOS type transistor 143. The drain of the fourth PMOS type transistor 134 is connected to the drain of the fourth NMOS type transistor 144. The source of the fourth NMOS type transistor 144 is connected to the drain of the fifth NMOS type transistor 145. The source of the fifth NMOS type transistor 145 is connected to the drain of the sixth NMOS type transistor 146. The source of the third NMOS type transistor 143 and the source of the sixth NMOS type transistor are connected to ground (0 volts).

The data hold unit 149 comprises a fourth inverter 147 and a fifth inverter 148. The input of the fourth inverter 147 and the output of the fifth inverter 148 are connected to the drain of the fourth PMOS type transistor 134. The output of the fourth inverter 147 and the input of the fifth inverter 148 are connected to the buffer unit 150.

The buffer unit 150 comprises a sixth inverter 151. The input of the sixth inverter 151 is connected to the output of the fourth inverter 147. The output of the sixth inverter 151 is connected to the data output 105.

The clock signal is inputted from the clock input 101. When the clock signal is at low level, the first NMOS type transistor 141 and the fourth NMOS type transistor 144 are placed in a non-conducting state and the first PMOS type transistor 131 is placed in a conducting state. The three inverters in the inverter unit 110 transform the clock signal from low level to high level. The high level signal places the third NMOS type transistor 143 and the sixth NMOS type transistor 146 in a conducting state, and places the third PMOS type transistor 133 in a non-conducting state. The node VI shown in FIG. 11 would be charged to high voltage, VDD (whose level is equivalent to the power source 104). The high voltage places the fourth PMOS type transistor 134 in a non-conducting state, and keeps the voltage value of the data output 105.

When the positive edge of the clock signal arrives, the first NMOS type transistor 141 and the fourth NMOS type transistor 144 are placed in a conducting state. The third NMOS type transistor 143 and the sixth NMOS type transistor 146 remain in the conducting state in a delay period which is determined by a delay time of the inverter unit 110. If the data signal from the data input 103 is at low level, the second PMOS type transistor 132 is placed in a conducting state, the node V1 is charged to high voltage, the fifth NMOS type transistor 145 is in a conducting state, and the fourth PMOS type transistor 134 is in a non-conducting state. The source of the fourth PMOS type transistor 134 is connected to ground through the fourth, fifth, and sixth NMOS type transistors 144, 145, 146. On the other hand, if the data signal from the data input 103 goes high, the second NMOS type transistor 142 is placed in a conducting state, the second PMOS type transistor 132 is in a non-conducting state, and the node V1 is connected to ground through the fourth, fifth, and sixth NMOS type transistors 144, 145, 146. Because the node V1 is at low level, the fourth PMOS type transistor 134 is placed in a conducting state, and the fifth NMOS type transistor 145 is in a non-conducting state. The drain of the fourth PMOS type transistor 134 outputs the high voltage to the data hold unit 149. In this period, the latch flip-flop is viewed as placed in a conducting state, and then the data signal from data input can be sampled and hold. Once the node CKDB shown in FIG. 11 turns to low level, the connection between the node V1 and data input is weaker and the latch flip-flop 130 is viewed as in a non-conducting state. After the negative edge of the clock signal arrives, the first PMOS type transistor 131 remains in a conducting state and the node V1 is held at high voltage VDD. The data signal from the data input 103 cannot be sampled.

Referring to FIG. 12, this is a sequence diagram of the hybrid latch flip-flop of FIG. 11. V(D), V(Clock), and V(Q) shown in FIG. 12 respectively represent the waveform diagram of the data input 103, the clock input 101, and the data output 105 of FIG. 11. As shown in FIG. 12, the data output 105 is at low level before Tn. When the positive edge of the clock signal arrives at Tn, the data input 103 is at high level, and this high level would be sampled and output to make the data output 105 change from low to high. Before Tn+1, the data input 103 is at low level, and the data output 105 is at high level. At Tn+1, the data input 103 remains at low level, and this low level is sampled and output to make the data output 105 change from high to low. Before Tn+2, the data input 103 is at low level and the data output is at low level too. At Tn+2, the low level of the data input 103 is sampled and the data output 105 remains at low level. Before Tn+3, the data input 103 is at high level and the data output 105 is at low level. At Tn+3, the high level of the data input 103 is sampled and the data output 105 changes from low to high. Before Tn+4, the data input 103 is at high level and the data output is at high level, too. At Tn+4, the high level of the data input 103 is sampled and the data output 105 remains at high level. Before Tn+5, the data input 103 is at low level and the data output 105 is at high level. At Tn+5, the low level of the data input 103 is sampled and the data output 105 changes from high to low.

When applying the hybrid latch flip-flop of the prior art to the driver circuit of the LCD, each column electrode and row electrode needs an exclusive hybrid latch flip-flop (HLFF) 100. However, the HLFF 100 comprises too many transistors and causes high power consumption in the driver circuit. In order to meet the requirement of low power consumption of the driver circuit, the HLFF applied in the LCD must have lower power consumption. On the other hand, a new HLFF design having the same function but lower power consumption is demanded.

According to the above description, to provide a new HLFF having lower power consumption is necessary.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a hybrid latch flip-flop that has lower power consumption.

In order to achieve the above-mentioned object, a hybrid latch flip-flop (HLFF) in accordance with the present invention includes a clock input, a negative pulse generating unit, a latch flip-flop, a buffer unit, a data input, and a data output. The latch flip-flop includes a sample unit and a hold unit. The clock input is connected to the negative pulse generating unit. The negative pulse generating unit is connected to the sample unit. The sample unit is connected to the hold unit. The hold unit is connected to the buffer unit. The data input is connected to the sample unit. The buffer unit is connected to the data output.

The negative pulse generating unit can be a positive edge trigger type, a negative edge trigger type, and a double edge trigger type. The sample unit includes seven transistors or six transistors.

Compared to the prior art, the advantages of the present invention is that the number of transistors in the sample unit is fewer, thus reducing power consumption. In the present invention, the negative pulse generating unit and the latch flip-flop are used separately, and the negative pulse generating unit is the common circuit in the driver circuit. Although the negative pulse generating unit has more transistors than the inverter unit of the prior art, the total number of transistors in the driver circuit of the present invention is fewer than in the prior art. Thus, the present invention achieves the object of reducing power consumption.

Furthermore, if adopting the double trigger, the data transmitting rate of the HLFF could be doubled compared to the data transmitting rate of the prior art.

Other objects, advantages, and novel features of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a hybrid latch flip-flop according to the preferred embodiment of the present invention, the hybrid latch flip-flop comprising a negative pulse generating unit and a latch flip-flop;

FIG. 2 is a circuit diagram of a first embodiment of a negative pulse generating unit of FIG. 1;

FIG. 3 is a circuit diagram of a second embodiment of the negative pulse generating unit of FIG. 1;

FIG. 4 is a circuit diagram of a third embodiment of the negative pulse generating unit of FIG. 1;

FIG. 5 is a circuit diagram of a first embodiment of the latch flip-flop of FIG. 1;

FIG. 6 is a circuit diagram of a second embodiment of the latch flip-flop of FIG. 1;

FIG. 7 is a circuit diagram of a third embodiment of the latch flip-flop of FIG. 1;

FIG. 8 is a circuit diagram of a fourth embodiment of the latch flip-flop of FIG. 1;

FIG. 9 is a block diagram of the HLFF applied in an LCD driving circuit according to the present invention;

FIG. 10 is a sequence diagram of the hybrid latch flip-flop of FIG. 1;

FIG. 11 is a block diagram of a hybrid latch flip-flop disclosed in the prior art; and

FIG. 12 is a sequence diagram of the hybrid latch flip-flop of FIG. 11.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Referring to FIG. 1, this is a block diagram of a hybrid latch flip-flop (HLFF) 300 according to the preferred embodiment of the present invention. The HLFF 300 includes a clock input 301, a negative pulse generating units 310, a latch flip-flop 330, a buffer unit 350, a data input 303, and a data output 305. The latch flip-flop 330 includes a sample unit 340 and a hold unit 349.

The clock input 301 is connected to the negative pulse generating unit 310. The negative pulse generating unit 310 is connected to the sample unit 340. The sample unit 340 is connected to the hold unit 349. The hold unit 349 is connected to the buffer unit 350. The data input 303 is connected to the sample unit 340. The buffer unit 350 is connected to the data output 305.

The negative pulse generating unit 310 receives the clock signal from the clock input 301, and transforms the clock signal to the negative pulse signal. The latch flip-flop 330 receives the negative pulse signal from the node 302. In the latch flip-flop 330, the sample unit 340 receives the data signal from the data input 303, and receives the negative pulse signal from the negative pulse generating unit 310. The sample unit 340 samples the data signal at each peak of the negative pulse signal. For example, at each peak of the negative pulse, if the data signal is at high level, the sample unit would output a high level signal. Otherwise, if the data signal is at low level, the sample unit would output a low level signal. The data signal being sampled would be sent to the hold unit 349 via the node 304. Before the next data sampling, the hold unit 349 would hold the sampled result from the sample unit 340 and output the sampled signal to the buffer unit 350 via the node 306. The buffer unit 350 delays and amplifies the sampled signal to provide a higher driving ability to drive the following circuit. Obviously, the HLFF 300 according to the present invention has the basic function like the conventional flip-flop. The basic function is to sample the data signal and output the sampled signal according to the clock signal. In the HLFF 300 according to the present invention, the negative pulse generating unit 310 includes at least three embodiments, and the latch flip-flop 330 includes at least four embodiments.

Referring to FIG. 2, this is a circuit diagram of the first embodiment of the negative pulse generating unit of FIG. 1. The negative pulse generating unit 410 includes a first inverter 411, a second inverter 412, a third inverter 413, a fourth inverter 414, and an AND gate 415. The input of the first inverter 411 is connected to the clock input 401. The output of the first inverter 411 is connected to the input of the second inverter 412. The output of the second inverter 412 is connected to the input of the third inverter 413. The output of the third inverter 413 is connected to one input of the AND gate 415. The other input of the AND gate 415 is connected to the clock input 401. The output of the AND gate 415 is connected to the input of the fourth inverter 414. The output of the fourth inverter 414 is connected to the node 402. The first inverter 411 and the second inverter 412 are used for delaying the clock signal, and the third inverter 413 is used for delaying and inverting the clock signal from the clock input 401. That means the clock signal would be delayed and inverted by the first, second and third inverters 411, 412, 413, and then input to one input of the AND gate 415. The clock signal from the clock input 401 is also input into the other input of the AND gate 415. The positive edge or the negative edge is directly input into one input of the AND gate 415, and the positive edge or the negative edge being delayed and inverted is also input into the other input of the AND gate 415. After receiving the positive edge of the clock signal and before receiving the delayed negative edge, the AND gate 415 outputs a positive voltage. These successive positive voltages would be viewed as a positive pulse. The positive pulse would be inverted to a negative pulse by the fourth inverter 414. The negative pulse is output to the node 402. However, after receiving the delayed negative edge of the clock signal and before receiving the positive edge, there would not be any pulse generated.

Referring to FIG. 3, this is a circuit diagram of the second embodiment of the negative pulse generating unit of FIG. 1. The negative pulse generating unit 510 includes a first inverter 511, a second inverter 512, a third inverter 513, a fourth inverter 514, and a NOR gate 516. The input of the first inverter 511 is connected to the clock input 501. The output of the first inverter 511 is connected to the input of the second inverter 512. The output of the second inverter 512 is connected to the input of the third inverter 513. The output of the third inverter 513 is connected to one input of the NOR gate 516. The other input of the NOR gate 516 is connected to the clock input 501. The output of the NOR gate 516 is connected to the input of the fourth inverter 514. The output of the fourth inverter 514 is connected to the node 502. The first inverter 511 and the second inverter 512 are used for delaying the clock signal, and the third inverter 513 is used for delaying and inverting the clock signal from the clock input 501. That means the clock signal would be delayed and inverted by the first, second and third inverters 511, 512, 513, and then input to one input of the NOR gate 516. The clock signal from the clock input 501 is also input into the other input of the NOR gate 516. The positive edge or the negative edge is directly input into one input of the NOR gate 516, and the positive edge or the negative edge being delayed and inverted is also input into the other input of the NOR gate 516. After receiving the negative edge of the clock signal and before receiving the delayed positive edge, the NOR gate 516 outputs a positive voltage. These successive positive voltages would be viewed as a positive pulse. The positive pulse would be inverted to a negative pulse by the fourth inverter 514. The negative pulse is output to the node 502. However, after receiving the delayed positive edge of the clock signal and before receiving the negative edge, there would not be any pulse generated.

Referring to FIG. 4, this is a circuit diagram of the third embodiment of the negative pulse generating unit of FIG. 1. It must be emphasized that the third embodiment of the negative pulse generating unit 610 adopts the double trigger method, and the data transmitting rate of the HLFF 300 could be double the data transmitting rate without changing the clock frequency. The negative pulse generating unit 610 includes a first inverter 611, a second inverter 612, a third inverter 613, a fourth inverter 614, and an Exclusive NOR gate 617. The input of the first inverter 611 is connected to the clock input 601. The output of the first inverter 611 is connected to the input of the second inverter 612. The output of the second inverter 612 is connected to the input of the third inverter 613. The output of the third inverter 613 is connected to one input of the Exclusive NOR gate 617. The other input of the Exclusive NOR gate 617 is connected to the clock input 601. The output of the Exclusive NOR gate 617 is connected to the input of the fourth inverter 614. The output of the fourth inverter 614 is connected to the node 602. The first inverter 611 and the second inverter 612 are used for delaying the clock signal, and the third inverter 613 is used for delaying and inverting the clock signal from the clock input 601. That means the clock signal would be delayed and inverted by the first, second and third inverters 611, 612, 613, and then input to one input of the Exclusive NOR gate 617. The clock signal from the clock input 601 is also input into the other input of the Exclusive NOR gate 617. The positive edge or the negative edge is directly input into one input of the Exclusive NOR gate 617, and the positive edge or the negative edge being delayed and inverted is also input into the other input of the Exclusive NOR gate 617. After receiving the negative edge of the clock signal and before receiving the delayed positive edge, or after receiving the positive edge of the clock signal and before receiving the delayed negative edge, the Exclusive NOR gate 617 outputs a positive voltage. These successive positive voltages would be viewed as a positive pulse. The positive pulse would be inverted to a negative pulse by the fourth inverter 614. The negative pulse is output to the node 602.

Referring to FIG. 5, this is a circuit diagram of the first embodiment of the latch flip-flop of FIG. 1. The latch flip-flop 730 comprises a sample unit 740 and a hold unit 749. The sample unit 740 comprises: four PMOS type transistors; which are a first PMOS type transistor 731, a second PMOS type transistor 732, a third PMOS type transistor 733, and a fourth PMOS type transistor 734; and three NMOS type transistors, which are a first NMOS type transistor 741, a second NMOS type transistor 742, and a third NMOS type transistor 743. The hold unit 749 includes a fifth inverter 747 and a sixth inverter 748.

The source of the first PMOS type transistor 731 and the source of the third PMOS type transistor 733 are connected to a power source VDD. The gate of the first PMOS type transistor 731, the gate of the first NMOS type transistor 741, and the gate of the third PMOS type transistor 733 all are connected to the pulse input 702. The gate of the second NMOS type transistor 742 and the gate of the second PMOS type transistor 732 are both connected to the data input 703. The drain of the first PMOS type transistor 731 is connected to the source of the second PMOS type transistor 732. The drain of the third PMOS type transistor 733 is connected to the source of the fourth PMOS type transistor 734. The node V7 is connected to the drain of the second PMOS type transistor 732, the drain of the first NMOS type transistor 741, the drain of the second NMOS type transistor 742, the gate of the third NMOS type transistor 743, and the gate of the fourth PMOS type transistor 734. The sources of the three NMOS type transistors 741, 742, 743 are connected to ground (0 volts). The drain of the third NMOS type transistor 743 and the drain of the fourth PMOS type transistor 734 are connected to the hold unit 749 via the node 704. As shown in FIG. 5, people skilled in the art could easily recognize that the first PMOS type transistor 731, the second PMOS type transistor 732, the first NMOS type transistor 741, and the second NMOS type transistor 742 constitute a NOR gate. The pulse input 702 and the data input 703 are two inputs of the NOR gate, and the node V7 is the output of the NOR gate. If the pulse input 702 is at high level, the node V7 would be at low level whether the data input 703 is at high level or low level. In such conditions, the fourth PMOS type transistor 734 is placed in a conducting state and the third NMOS type transistor 743 is in a non-conducting state. The pulse input 702 being at high level also places the third PMOS type transistor 733 in a non-conducting state, and then the hold unit 749 holds the same data. In addition, if the pulse input 702 is at low level and the data input 703 is also at low level, the node V7 would be at high level. Otherwise, if the pulse input 702 is at low level and the data input 703 is at high level, the node V7 would be at low level. When the node V7 is at high level, the fourth PMOS type transistor 734 is placed in a non-conducting state and the third NMOS type transistor 743 is in a conducting state. The hold unit 749 is connected to ground through the node 704 and the third NMOS type transistor 743. This is equal to outputting a low voltage to the hold unit 749. On the other hand, when the node V7 is at low level, the fourth PMOS type transistor 734 is placed in a conducting state and the third NMOS type transistor 743 is in a non-conducting state. Due to the low level at the pulse input 702, the third PMOS type transistor 733 is placed in a conducting state. Then, a high voltage would transmit to the hold unit 749. The negative edge of the clock signal would trigger the sample unit 740, and then the data signal from the data input is sampled. The hold unit 749 receives the sampled data signal from the sample unit 740 via the node 704. Before the next data are sampled, the hold unit 749 inverts and holds the sampled data, and then outputs the sampled data to the buffer unit 750 via the node 706.

The buffer unit 750 includes a seventh inverter 751, which is used for inverting the inverted sampled data from the latch flip-flop 730 and the node 706. Then, the inverted sampled data are transformed to the original sampled data. The buffer unit 750 outputs the sampled data to the node 705. That means the buffer unit 750 can provide the function of buffering the output data, and provide the higher driving force to the following circuit.

Referring to FIG. 6, this is a circuit diagram of the second embodiment of the latch flip-flop of FIG. 1. The latch flip-flop 830 comprises a sample unit 840 and a hold unit 849. The sample unit 840 comprises: four PMOS type transistors, which are a first PMOS type transistor 831, a second PMOS type transistor 832, a third PMOS type transistor 833, and a fourth PMOS type transistor 834; and three NMOS type transistors, which are a first NMOS type transistor 841, a second NMOS type transistor 842, and a third NMOS type transistor 843. The hold unit 849 includes a fifth inverter 847 and a sixth inverter 848.

The source of the first PMOS type transistor 831 and the source of the third PMOS type transistor 833 are connected to a power source VDD. The gate of the first PMOS type transistor 831 and the gate of the second NMOS type transistor 842 are connected to the data input 803. The gate of the first NMOS type transistor 841, the gate of the second PMOS type transistor 832, and the gate of the fourth PMOS type transistor 834 all are connected to the pulse input 802. The drain of the first PMOS type transistor 831 is connected to the source of the second PMOS type transistor 832. The drain of the third PMOS type transistor 833 is connected to the source of the fourth PMOS type transistor 834. The node V8 is connected to the drain of the second PMOS type transistor 832, the drain of the first NMOS type transistor 841, the drain of the second NMOS type transistor 842, the gate of the third NMOS type transistor 843, and the gate of the third PMOS type transistor 833. The sources of the three NMOS type transistors 841, 842, 843 are connected to ground (0 volts). The drain of the third NMOS type transistor 843 and the drain of the fourth NMOS type transistor 844 are connected to the hold unit 849 via the node 804. As shown in FIG. 5, people skilled in the art could easily recognize that the first PMOS type transistor 831, the second PMOS type transistor 832, the first NMOS type transistor 841, and the second NMOS type transistor 842 constitute a NAND gate. The pulse input 802 and the data input 803 are two inputs of the NAND gate, and the node V8 is the output of the NAND gate. If the pulse input 802 is at high level, the node V8 would be at low level whether the data input 803 is at high level or low level. In such conditions, the third PMOS type transistor 833 is placed in a conducting state and the third NMOS type transistor 843 is in a non-conducting state. The pulse input 802 being at high level also places the fourth PMOS type transistor 834 in a non-conducting state, and then the hold unit 749 holds the same data. In addition, if the pulse input 802 is at low level and the data input 803 is also at low level, the node V8 would be at high level. Otherwise, if the pulse input 802 is at low level and the data input 803 is at high level, the node V8 would be at low level. When the node V8 is at high level, the third PMOS type transistor 833 is placed in a non-conducting state and the third NMOS type transistor 843 is in a conducting state. The hold unit 849 is connected to ground through the node 804 and the third NMOS type transistor 843. This is equal to outputting a low voltage to the hold unit 849. On the other hand, when the node V8 is at low level, the third PMOS type transistor 833 is placed in a conducting state and the third NMOS type transistor 843 is in a non-conducting state. Due to the low level at the pulse input 802, the fourth PMOS type transistor 834 is placed in a conducting state. Then, a high voltage would transmit to the hold unit 849. The negative edge of the clock signal would trigger the sample unit 840, and then the data signal from the data input is sampled. The hold unit 849 receives the sampled data signal from the sample unit 840 via the node 804. Before the next data are sampled, the hold unit 849 inverts and holds the sampled data, and then outputs the sampled data to the buffer unit 850 via the node 806.

The buffer unit 850 includes a seventh inverter 851, which is used for inverting the inverted sampled data from the latch flip-flop 830 and the node 806. Then, the inverted sampled data are transformed to the original sampled data. The buffer unit 850 outputs the sampled data to the node 805. That means the buffer unit 850 can provide the function of buffering the output data, and provide the higher driving force to the following circuit.

The sample units 740 and 840 described above each include seven MOS type transistors. Since the sampling process according to the present invention adopts negative pulse signal triggering, the pulse input 802 is mostly at low level and the node V8 is mostly at high level. Thus, in most implementations, adopting only the first NMOS type transistor 841 is good enough, and better than adopting both the first NMOS type transistor 841 and the second NMOS type transistor 842. By this means, the number of transistors in the latch flip-flop is further decreased.

Referring to FIG. 7, this is a circuit diagram of the third embodiment of the latch flip-flop of FIG. 1. The latch flip-flop 930 comprises a sample unit 940 and a hold unit 949. The sample unit 940 comprises: four PMOS type transistors, which are a first PMOS type transistor 931, a second PMOS type transistor 932, a third PMOS type transistor 933, and a fourth PMOS type transistor 934; and two NMOS type transistors, which are a first NMOS type transistor 941 and a second NMOS type transistor 942. The hold unit 949 includes a fifth inverter 947 and a sixth inverter 948.

The source of first PMOS type transistor 931 and the source of the third PMOS type transistor 933 are connected to a power source VDD. The gate of the first PMOS type transistor 931, the gate of the first NMOS type transistor 941, and the gate of the third PMOS type transistor 933 are connected to the node 902. The gate of the second PMOS type transistor 932 is connected to the data input 903. The drain of the first PMOS type transistor 931 is connected to the source of the second PMOS type transistor 932. The drain of the third PMOS type transistor 933 is connected to the source of the fourth PMOS type transistor 934. The node V9 is connected to the drain of the second PMOS type transistor 932, the drain of the first NMOS type transistor 941, the gate of the second NMOS type transistor 942, and the gate of the fourth PMOS type transistor 934. The source of the first NMOS type transistor 941 and the source of the second NMOS type transistor 942 are connected to ground (0 volts). The drain of the second NMOS type transistor 942 and the drain of the fourth PMOS type transistor 934 are connected to the hold unit 949 via the node 904. If the node 902 is at high level, the first PMOS type transistor 931 is placed in a non-conducting state, the third PMOS type transistor 933 is in a non-conducting state, and the first NMOS type transistor is in a conducting state. The high level of the node V9 is connected to ground via the first NMOS type transistor 941, and is discharged to a low level. Due to the node V9 being at low level, the fourth PMOS type transistor 934 is placed in a conducting state and the second PMOS type transistor 932 is in a non-conducting state. Then, the hold unit 949 holds the same data whether the data input 903 is at high level or low level. When the node 902 is at low level, the first PMOS type transistor 931 is placed in conducting state, the third PMOS type transistor 933 is in a conducting state, and the first NMOS type transistor 941 is in a non-conducting state. If the data input 903 is at low level at that moment, the second PMOS type transistor 932 would be placed in a conducting state. The node V9 is charged to a high level, and the fourth PMOS type transistor 934 is placed in a non-conducting state and the second NMOS type transistor 942 is in a conducting state. The hold unit 949 is connected to ground through the node 904 and the second NMOS type transistor 942. The equivalent is to output a low voltage to the hold unit 949. If the data input 903 is at high level, the second PMOS type transistor 932 is placed in a non-conducting state. The node V9 is connected to ground. Thus, the fourth PMOS type transistor 934 is placed in a conducting state and the second NMOS type transistor 942 is in a non-conducting state. Assuming that the third PMOS type transistor 933 is also in a conducting state, the node 904 is successively charged to a high level, and outputs the high voltage to the hold unit 949. The negative edge of the clock signal would trigger the sample unit 940, and then the data signal from the data input 903 is sampled. The hold unit 949 receives the sampled data signal from the sample unit 940 via the node 904. Before the next data are sampled, the hold unit 949 inverts and hold the sampled data, and then outputs the sampled data to the buffer unit 950 via the node 906.

The buffer unit 950 includes a seventh inverter 951, which is used for inverting the inverted sampled data from the latch flip-flop 930 and the node 906. Then, the inverted sampled data are transformed to the original sampled data. The buffer unit 950 outputs the sampled data to the node 905. That means the buffer unit 950 can provide the function of buffering the output data, and provide the higher driving force to the following circuit.

Referring to FIG. 8, this is a circuit diagram of the fourth embodiment of the latch flip-flop of FIG. 1. The latch flip-flop 1030 comprises a sample unit 1040 and a hold unit 1049. The sample unit 1040 comprises: four PMOS type transistors, which are a first PMOS type transistor 1031, a second PMOS type transistor 1032, a third PMOS type transistor 1033, and a fourth PMOS type transistor 1034; and two NMOS type transistors, which are a first NMOS type transistor 1041 and a second NMOS type transistor 1042. The hold unit 1049 includes a fifth inverter 1047 and a sixth inverter 1048.

The source of first PMOS type transistor 1031 and the source of third PMOS type transistor 1033 are connected to a power source VDD. The gate of the first PMOS type transistor 1031 and the gate of the first NMOS type transistor 1041 are connected to the data input 1003. The drain of the first PMOS type transistor 1031 is connected to the source of the second NMOS type transistor 1042. The drain of the third PMOS type transistor 1033 is connected to the source of the fourth PMOS type transistor 1034. The gate of the second PMOS type transistor 1032 and the gate of fourth PMOS type transistor 1034 are connected to the node 1002. The drain of first PMOS type transistor 1031 is connected to the source of the second PMOS type transistor 1032. The drain of third PMOS type transistor 1033 is connected to the source of the fourth PMOS type transistor 1034. The node V10 is connected to the drain of the second PMOS type transistor 1032, the drain of the first NMOS type transistor 1041, the gate of the second NMOS type transistor 1042, and the gate of the third PMOS type transistor 1033. The source of the first NMOS type transistor 1041 and the source of the second NMOS type transistor 1042 are connected to ground (0 volts). The drain of the second NMOS type transistor 1042 and the drain of the fourth PMOS type transistor 1034 are connected to the hold unit 1049 via the node 1004. If the node 1002 is at high level, the second PMOS type transistor 1032 and the fourth PMOS type transistor 1034 would be placed in a non-conducting state. If the data input 1003 is at high level, the first PMOS type transistor 1031 would be placed in the non-conducting state and the first NMOS type transistor 1041 would be placed in the conducting state. That causes the node V10 to connect to ground via the first NMOS type transistor 1041. When the node V10 is at low level, the third PMOS type transistor 1033 is placed in a conducting state and the second NMOS type transistor 1044 is in a non-conducting state. Then, the hold unit 1049 holds the same data whether the data input is at high level or low level. If the data input 1003 is at low level, the second PMOS type transistor 1032 would be placed in a conducting state and the fourth PMOS type transistor 1034 would be placed in a conducting state. If the data input is at low level at that moment, the first NMOS type transistor 1041 would be placed in the non-conducting state and the first PMOS type transistor 1031 would be placed in a conducting state. The node V10 is successively charged to a high level. Due to the high level of the node V10, the third PMOS type transistor 1033 would be placed in a non-conducting state and the second NMOS type transistor 1042 would be placed in a conducting state. According to the above, the hold unit 1049 is connected to ground through the node 1004 and the second NMOS type transistor 1042. The equivalent is to output a low voltage to the hold unit 1049. If the data input 1003 is at high level, the first PMOS type transistor 1031 would be placed in a non-conducting state and the first NMOS type transistor 1041 would be placed in a conducting state. The node V10 is connected to ground via the second NMOS type transistor 1042. Thus, the third PMOS type transistor 1033 is placed in a conducting state and the second NMOS type transistor 1042 is in a non-conducting state. The node 1004 is successively charged to a high level, and outputs the high voltage to the hold unit 1049. The negative edge of the clock signal would trigger the sample unit 1040, and then the data signal from the data input 1003 is sampled. The hold unit 1049 receives the sampled data signal from the sample unit 1040 via the node 1004. Before the next data are sampled, the hold unit 1049 inverts and holds the sampled data, and then outputs the sampled data to the buffer unit 1050 via the node 1006.

The buffer unit 1050 includes a seventh inverter 1051, which is used for inverting the inverted sampled data from the latch flip-flop 1030 and the node 1006. Then, the inverted sampled data are transformed to the original sampled data. The buffer unit 1050 outputs the sampled data to the node 1005. That means the buffer unit 1050 can provide the function of buffering the output data, and provide the higher driving force to the following circuit.

The sample units 740 and 840 described above each include seven MOS type transistors, and the sample units 940 and 1040 described above each include six MOS type transistors. Compared to the sample unit 140 of FIG. 11, which has ten MOS type transistors, the sample unit according to the present invention has lower power consumption. Although the number of transistors of the negative pulse generating unit 310 of the present invention is more than the number of transistors of the inverter unit 110 of FIG. 11, the negative pulse generating unit 310 and the latch flip-flop according to the present invention can be separated to let the negative pulse generating unit 310 be the common circuit in the driving circuit. Referring to FIG. 9, this is a block diagram of the HLFF applied in an LCD driving circuit according to the present invention. The negative pulse generating unit is the common circuit in the LCD driving circuit, therefore the increase in the number of transistors from the negative pulse generating unit will not cause increased power consumption of the total driving circuit. Thus, the HLFF according to the present invention achieves the object of having lower power consumption than the prior art.

Referring to FIG. 10, this is a sequence diagram of the hybrid latch flip-flop of FIG. 1. In FIG. 10, V(D) represents the waveform diagram of the data input 303, V(Clock) represents the waveform diagram of the clock input 301, V(CLK) represents the waveform diagram of the pulse input 302, and V(Q) represents the waveform diagram of the data output 305. V(CLK) is generated by the negative pulse generating unit of FIG. 4. As shown in FIG. 10, V(CLK) and V(Clock) are at low level before clock time Tn. When the negative edge of V(Clock) arrives at Tn, V(CLK) generates a negative pulse and V(D) is sampled. Because V(D) is at high level, V(Q) changes from low to high level. Before Tn+1, V(D) is at low level, and V(Q) is at high level. At Tn+1, another negative edge of V(Clock) arrives, and V(CLK) generates another negative pulse and V(D) is sampled. Because V(D) is at low level, V(Q) changes from high to low level. For this reason, at Tn+2, because V(D) is at low level, V(Q) remains at low level. At Tn+3, because V(D) is at high level, V(Q) changes from low to high level. At Tn+4, because V(D) is at high level, V(Q) remains at high level. At Tn+5, because V(D) is at low level, V(Q) changes from high to low level. Although the embodiments described above are applied in the LCD driving circuit, people skilled in the art would know that the present invention can be applied in many fields according to the disclosure above. The present invention should not be limited to the LCD driving circuit.

It is to be further understood that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. 

1. A hybrid latch flip-flop, comprising: a negative pulse generating unit; a clock input connected to the negative pulse generating unit for applying clock signals to the negative pulse generating unit; a latch flip-flop connected to the negative pulse generating unit, the latch flip-flop comprising a sample unit and a hold unit, an output of the sample unit connected to the hold unit; a buffer unit connected to the hold unit; a data input unit connected to an input of the sample unit for applying data signals to the sample unit; and a data output connected to the buffer unit for outputting the signals.
 2. The hybrid latch flip-flop of claim 1, wherein the negative pulse generating unit is a positive edge trigger type.
 3. The hybrid latch flip-flop of claim 1, wherein the negative pulse generating unit is a negative edge trigger type.
 4. The hybrid latch flip-flop of claim 1, wherein the negative pulse generating unit is a double-edge trigger type.
 5. The hybrid latch flip-flop of claim 1, wherein the sample unit comprises seven transistors.
 6. The hybrid latch flip-flop of claim 5, wherein the sample unit comprises three PMOS type transistors and four NMOS type transistors.
 7. The hybrid latch flip-flop of claim 1, wherein the sample unit comprises six transistors.
 8. The hybrid latch flip-flop of claim 7, wherein the sample unit comprises two PMOS type transistors and four NMOS type transistors. 